Which effluent treatment phase targets the removal of both nitrogen and phosphorus?

The correct answer is tertiary treatment, which is the advanced phase of wastewater treatment that focuses on removing nutrients, specifically nitrogen and phosphorus, from effluent. This phase occurs after primary treatment, which removes solids and secondary treatment, which mainly focuses on the biological degradation of organic matter.

During tertiary treatment, various processes such as chemical precipitation, biological nutrient removal, and advanced filtration may be employed to effectively reduce the concentrations of nitrogen and phosphorus compounds in the water. The removal of these nutrients is vital for preventing problems like eutrophication in receiving water bodies, which can lead to algal blooms and significant ecosystem disruption.

In contrast, primary treatment primarily focuses on the removal of large solids and floatable materials while secondary treatment primarily deals with organic matter using biological processes. Neither of these earlier phases directly targets nutrient removal, which is why they do not fulfill the conditions of the question.